Such a method and such a device are known from DE 10 2005 042 926. In the known method, used compressed air from a hollow body manufacturing machine, for example, a stretch blow-molding machine, is fed back for reuse. Stretch blow-molding machines require a relatively high proportion of compressed air in order to blow up prefabricated and heated bottle preforms into finished containers. The air used for the blowing procedure has a pressure that is reduced after the blowing procedure, but this pressure is still relatively high. In order to prevent this pressure from being wasted, the compressed air is fed back into the pressure generator (compressor) after the containers have been blown. It is detrimental thereby that the return feed must take place at a certain minimum pressure in order to allow a feed in. It is consequently not possible to recycle all the compressed air that arises.
Because different processes are run in the blowing process of the stretch blow-molding machine, compressed air at different pressures arises, and of this air, only that portion that lies above the minimum pressure can be reused by the known method.